[Q] How to get best battery life (G2)

I've been reading a lot on customr ROM's for the G2 (I have a D802) but I was wondering what you take was on the following dilemma. One of the most important things for me is to maximize the battery life but I would also like to have a lot of customizing options. Therefore, at the least the way I see it, I have the following 2 choices:

A)
Root + improved kernel + install Xposed Framework

B)
Root + Custom ROM (CM11, PA, ...)

Maybe it's even possible/necessary to install the Xposed framework on top of the custom ROM?

What would result in the best battery life experience, stock rom or custom ROM?

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